Air bag and air bag apparatus

ABSTRACT

An air bag body ( 1 ) is expanded by charging air therein after being expanded in a flat surface shape. Next, by gently gripping the air bag body ( 1 ) by upper and lower blades ( 26, 25 ) radially arranged in a radial direction of the air bag body ( 1 ), height in a radial direction of the air bag body ( 1 ) is linearly restricted along the upper and lower blades ( 26, 25 ). Next, a plurality of movable blocks ( 24 ) are forward moved toward a center of the air bag body ( 1 ), and upper and lower panels ( 12, 11 ) of the air bag body ( 1 ) are accumulated. At this time, the upper and lower panels ( 12, 11 ) of the air bag body ( 1 ) are folded in a state of being apart from each other so as to form a wave shape. Next, the air bag body ( 1 ) is rotated, a portion left in a tab shape is wound around a periphery, and a center protruding portion of the air bag body ( 1 ) is pressed from an upper side, whereby a front surface deploying portion ( 35 ) is formed. When supplying gas to the folded air bag body ( 1 ), the front surface deploying portion ( 35 ) rapidly deploys so as to break a cover ( 5 ) and the gas is smoothly supplied to a peripheral edge portion ( 14 ), whereby it is possible to smoothly and rapidly deploy the air bag body ( 1 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an air bag expanding and deploying dueto an inflow of gas, and an air bag apparatus.

2. Description of the Related Art

Conventionally, there has been known, for example, an air bag apparatusprovided in a steering wheel of a motor vehicle. The air bag apparatusis provided with an air bag body formed in a flat bag shape, a covercovering the air bag body, an inflator injecting gas, and the like.Then, the air bag body is folded to be small in accordance with acertain method at unactivated state so as to be received inside thecover. At a time of detecting an impact of collision by a collisionsensor, the air bag body is expanded by injecting the gas from theinflator. The cover is broken due to an expansion pressure of the airbag body and the air bag body is protruded, expanded and deployed toface the passenger, so that the impact of the collision to a passengeris reduced.

The air bag body has been conventionally folded along a straight line ata predetermined position from a state being expanded on a flat plate soas to be formed in a rectangular parallelepiped shape capable of beingreceived in the cover. However, there is a problem that it is hard tomechanically produce the folded air bag body, a lot of labor is requiredand it is hard to improve the productivity.

In order to improve the above mentioned points, as a folding methodsuitable for automation, for example, there has been known a structureshown in International Patent Publication Laid-Open No. WO97/48580. Inparticular, the air bag body is expanded during a folding process byusing a folding apparatus provided with a folding plate arranged so asto form a coaxial circle shape or a spiral shape in opposition to eachother from upper and lower portions of the air bag body. The air bagbody is folded by gripping the air bag body by the folding plates, andmoving or deforming the folding plates toward a predetermined hollowspace so as to reduce radial distance between each of adjacent foldingplates. However, in this structure, there is a problem that thestructure of the apparatus becomes complex and it is not easy to reducethe production cost.

Further, with respect to, for example, the air bag body formed in a flatcircular shape, there has been proposed a so-called petal fold in whichthe air bag body is collected toward a center from an outer peripheralportion thereof so as to form a pleat shape. With respect to thismethod, there have been known structures described in Japanese PatentPublication Laid-Open Nos. 10-129381, 10-217894 and the like.

At present, there is required a structure of an air bag body which canimprove the deploying characteristic and reduce the production cost.

SUMMARY OF THE INVENTION

The present invention is made by taking the points mentioned above intoconsideration, and an object of the present invention is to provide anair bag and an air bag apparatus in which the deploying characteristicof the airbag is improved and the production cost can be reduced.

The first aspect of the invention provides an air bag comprising: afirst surface portion with an inlet port through which gas is introducedinto the air bag; a second surface portion opposed to the first surfaceportion; wherein the first surface portion and the second surfaceportion are respectively accumulated and folded in a pleat-like foldtoward the inlet port with the surface portions being substantiallydetached from each other, a plurality of tab portions formed along theinlet port in a spiral shape, the first surface portion and the secondsurface portion linearly opposed to each other at the tab portions.

The second aspect of the invention provides an air bag apparatuscomprising: an air bag body; an accommodating container receiving anfolded air bag and being breakable at a predetermined condition, the airbag comprising: a first surface portion with an inlet port through whichgas is introduced into the air bag; a second surface portion opposed tothe first surface portion; wherein the first surface portion and thesecond surface portion are respectively accumulated and folded in pleatstoward the inlet port with the surface portions being substantiallydetached from each other, a plurality of tab portions formed along theinlet port in a spiral shape, the first surface portion and the secondsurface portion linearly opposed to each other at the tab portions.

The third aspect of the invention provides an air bag according toaforementioned aspects of the invention, wherein the second surfaceportion is formed in a substantially single layer at a part opposing tothe inlet port of the first surface portion, wherein the second surfaceportion includes a portion opposing to the inlet port of the firstsurface portion and has a front surface deploying portion deployable ina direction to a front side of the air bag, wherein the first surfaceportion is opposed to and is substantially detached from the secondsurface portion at a part distant from the inlet port, and wherein thefront surface deploying portion is accumulated and folded toward theinlet port without substantially engaging with the tab portion, and isdeployable in a direction moving apart from the inlet port.

According to aforementioned aspects of the invention, at the tabportion, the gas is smoothly supplied to an end portion of the tabportion along the linearly opposing portion, and the tab portion isdeployed so as to be unwound. Accordingly, the gas introduced from theinlet port is smoothly supplied to a peripheral edge portion, and thedeploying characteristic of the air bag body is improved. Further, thefront surface deploying portion can rapidly deploy to a side of thebreaking portion immediately after the inflow of the gas, to break thecover covering the folded air bag body and efficiently deploy the airbag body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view showing one embodiment of an air bag bodyin accordance with the present invention, and shows a folded state ofthe air bag body; FIG. 1B is a cross sectional view showing a state ofcombining a cover with the air bag body;

FIG. 2 is a partially cutaway view in perspective showing a state ofcombining a retainer with the air bag body;

FIG. 3 is a perspective view of a part of a folding apparatus of the airbag body;

FIG. 4 is a perspective view showing a folding step of the air bag body;

FIG. 5 is a perspective view showing a folding step of the air bag bodysubsequent to FIG. 4;

FIG. 6 is a perspective view showing a folding step of the air bag bodysubsequent to FIG.5;

FIG. 7 is a perspective view showing a folding step of the air bag bodysubsequent to FIG. 6;

FIG. 8 is a cross sectional view along a line VIII—VIII in FIG. 7;

FIG. 9 is a cross sectional view showing a folding step of the air bagbody subsequent to FIG. 8;

FIG. 10 is a perspective view showing a folding step of the air bag bodysubsequent to FIG. 7;

FIG. 11 is a cross sectional view along a line XI—XI in FIG. 10;

FIG. 12 is a perspective view schematically showing an outer appearanceof the air bag body in FIG. 10;

FIG. 13 is a perspective view showing a folding step of the air bag bodysubsequent to FIG. 10;

FIG. 14 is a perspective view schematically showing an outer appearanceof the air bag body in FIG. 13;

FIG. 15 is a perspective view showing a folding step of the air bag bodysubsequent to FIG. 13;

FIG. 16 is a cross sectional view along a line XVI—XVI in FIG. 15;

FIG. 17 is a perspective view showing another embodiment of an air bagbody in accordance with the present invention; and

FIG. 18 is a cross sectional view along a line XVIII—XVIII in FIG. 17.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A description will be given by following embodiments of an air bag andan air bag apparatus in accordance with the present invention withreference to the accompanying drawings.

In FIGS. 1A, 1B and 2, an air bag body 1 is assembled in an air bagapparatus corresponding to an occupant restraint apparatus provided in aboss portion of a steering wheel of a motor vehicle. The air bagapparatus is also called as an air bag module, and is constituted by aretainer 3 formed in a substantially ring shape and provided with a studbolt 3 a in a protruding manner, a base plate corresponding to a memberto be mounted, a cover 5 having a breakable seam 5 a and made of asynthetic resin or the like, an inflator injecting gas and the like inaddition to the air bag body 1 (some of the constituting members are notillustrated). Further, the air bag apparatus protects the passenger froman impact of collision by injecting the gas from the inflator, expandingthe air bag body 1 received in a folding manner, breaking the cover 5along a predetermined tear-line due to an expansion pressure of the airbag body 1 so as to protrude the air bag body 1, and widely deployingthe air bag body 1 in front of the passenger.

As shown in FIG. 2, the air bag body 1 is formed in a flat bag shape bysewing two circular base fabrics having substantially the same shape.That is, the air bag body 1 is formed by overlapping a lower panel (alower base fabric panel) 11 provided with a gas introduction surfacecorresponding to a first surface portion and an upper panel (an upperbase fabric panel) 12 provided with a surface opposed to the gasintroduction surface and corresponding to a second surface portion,sewing a peripheral edge portion 14 and making it inside out through aninlet port 15 for inserting the inflator, the inlet port 15 having acircular hole shape and formed in a center of the lower panel 11. Thediameter of a hole in a center of the retainer 3 is substantially equalto that of the hole of the inlet port 15. Further, a plurality ofmounting holes 16 into which the stud bolts 3 a are inserted is formedon the lower panel 11 at positions around the inlet port 15corresponding to a gas introduction port through which the gas isintroduced by the inflator. A part of the lower panel 11 around theinlet port 15 is reinforced by an annular reinforcing fabric 18. Asingle vent hole or a plurality of vent-holes (not shown) forventilating the gas introduced by the inflator is formed on the lowerpanel 11. In the present embodiment, each of the panels 11 and 12 isformed by a so-called “non-coat” base fabric having a diameter of 650mm, using a yarn of 66-nylon and 315 denier with 200 g/m2 and having noelastomer coatings, for example.

As shown in FIGS. 6-8 and 13, the folding apparatus 21 is constituted bya table 22, a center block 23 corresponding to expanding means andpressing means, a plurality of movable blocks 24 corresponding toaccumulating means, a lower blade 25 and an upper blade 26 correspondingto a guide member, a center plate 27 corresponding to displacing means,control means (not shown) controlling these elements, an electric powersource apparatus, a drive source and the like.

The table 22 is provided with a substantially flat plate surface(hereinafter, the plate surface of the table 22 is referred as areference surface S) on an upper surface thereof, and as shown in FIG.3, a center block 23 is placed in a circular hole 22 a provided in acenter portion of the plate surface. The center block 23 is providedwith a circular column portion 23 a having a shape similar to theinflator and a peripheral edge portion 23 b surrounding the circularcolumn portion 23 a and coaxially provided at a position lower than thecircular column portion 23 a. Further, the center block 23 is structuredsuch that a rotating mechanism rotating at an optionally set angle up toabout 90 degrees and a vertically moving mechanism vertically moving atan optionally set stroke up to about 160 mm are combined. An air nozzle(not shown) injecting the air is installed in the center block 23.Holding portions 23 c each having a circular hole shape and capable ofinserting the stud bolt 3 a of the retainer 3 so as to affix the studbolt are formed in the peripheral edge portion 23 b at a predeterminedinterval. In this case, in the respective drawings, for explanationpurpose, the table 22 and the center block 23 are omitted.

As shown in FIG. 3, a plurality of slit portions 22 b are radiallyformed around the circular hole 22 a on the table 22, and a lower blade25 having a flat plate shape and being vertical with respect to thereference surface S is provided in each of the slit portions 22 b insuch a manner as to move outward and inward in a vertical direction,more particularly, in such a manner as to move from the plate surface ofthe table 22 to a predetermined height. Further, a guide portion 25 aparallel to the reference surface S is provided in each of the lowerblades 25 along an upper end edge portion. An end portion of the guideportion 25 a, that is, a comer portion between an inner peripheral sideand an outer peripheral side of each of the lower blades 25, is formedin a smooth curved surface.

As shown in FIG. 7 for example, movable blocks 24 are respectivelyprovided at a position between the lower blades 25. Each of the movableblocks 24 is connected to driving means arranged under the table 22 viaa slit (not shown) provided on the table 22, and is guided and driven soas to move forward and backward from the peripheral edge portion of thetable 22 to a portion near the center block 23, that is, each of themovable blocks can be collected and distributed. Further, each of themovable blocks 24 is formed in a substantially fan shape in plan, and apressing portion 24 a is provided in an end portion in the innerperipheral side thereof opposed to the center block 23, for example, ina curved surface shape.

A plurality of upper blades 26 is radially mounted on a lower surface ofan upper plate 29 provided above the table 22 as shown in FIG. 6, andthose upper blades are moved and driven in a vertical direction togetherwith the upper plate 29. Further, each of the upper blades 26 isarranged so as to oppose a corresponding lower blade 25, and pairs ofcorresponding upper and lower blades 26 and 25 have end edges aligned toform an opposed line. A pair of upper and lower blades 26 and 25 isalternately arranged with the movable block 24 in a circumferentialdirection. The upper blade 26 has a plate shape, which is similar to thelower blade 25, vertical with respect to the reference surface S, and anend portion, that is, a corner portion thereof having a smooth curvedsurface shape. Further, a guide portion 26 a parallel to the guideportion 25 a of the lower blade 25 is formed in the upper blade 26 so asto oppose the guide portion 25 a. The length of each of the upper blades26 is substantially the same as that of the lower blades 25, however,the height thereof is formed to be larger than that of the lower blades25. The upper plate 29 is provided with support portions 29 b supportingeach of the upper blades 26 and arranged so as to form a radial shape inplan, an inner peripheral side connecting portion 29 c connecting endportions in an inner peripheral side of the support portions 29 b toeach other, and an outer peripheral side connecting portion 29 dconnecting end portions in an outer peripheral side of the supportportions 29 b to each other.

In this case, an emboss work is applied to end portions 26 a and 25 a atwhich the upper and lower blades 26 and 25 are linearly in contact withthe air bag body 1, or an elastomer tape or the like is adhered thereto,whereby these portions are slidably in contact with the air bag body 1with a suitable sliding resistance.

In accordance with the present embodiment, eight movable blocks 24 andeight pairs of upper and lower blades 26 and 25 corresponding theretoare provided. In the case of the structure which does not cover theregion above the inlet port 15 of the air bag body 1, the number ofthese elements can be suitably selected taking into account the size ofthe air bag body 1 and the shape of a space in which the air bag body 1is received.

Further, a circular hole 29 a is pierced in the center portion of theupper plate 29, and a disc-like center plate 27 (refer to FIG. 13)having substantially the same diameter as that of the circular hole 29 aand vertically driven independent from the upper plate 29 is arrangedwithin the circular hole 29 a.

Next, a description will be given of a folding step of the air bag 1with reference to FIGS. 1A to 16. In this case, in FIGS. 3 to 6, themovable blocks 24 are omitted.

In an initial state, the center block 23 is arranged so that a backsurface of the peripheral edge portion 23 b is connected parallel to afront surface of the table 22, as shown in FIG. 3. Further, the lowerblades 25 are retracted downward from the back surface of the table 22,the upper blades 26 and the center plate 27 are retracted upward and themovable blocks 24 are retracted to the outer peripheral side. Withrespect to the air bag body 1, as shown in FIG. 2, the retainer 3 ispreviously inserted into an inner portion of the air bag body 1 from theinlet port and the stud bolts 3 a are extended out from the mountingholes 16, as shown in FIG. 2. After the above mentioned state, the airbag body 1 is expanded on the table 22 so as to form a flat plate andset in a stationary manner, as shown in FIG. 4, and the circular columnportion 23 a of the center block 23 is inserted into the inlet port 15.Further, each of the stud bolts 3 a is inserted in one holding portion23 c and is fixed by a lock mechanism (not shown) provided in theholding portion 23 c.

Next, as shown in FIG. 5, as an expanding step, compressed air is bledinto the air bag body 1 from an air nozzle, as shown by an arrow A,provided in the circular column portion 23 a of the center block 23 soas to form the air bag body 1 in an flat cushion shape. Here, in thisstate, the air bag body 1 is in a state of being expanded so as to besofter than a hardness of the air bag body 1 in a complete expandingstate such as the state at a time of deploying the air bag body 1.

Next, as shown in FIG. 6, as the restricting step, the lower blades 25are ascended and protruded upward from the surface of the table 22, andthe upper blades 26 are descended so as to be brought into contact withthe air bag body 1. Further, as shown in FIGS. 7 and 8, the air bag body1 is held between the lower blades 25 and the upper blades 26 so as tobe radially depressed In this state, a predetermined interval is setbetween the guide portions in the upper and lower blades 26 and 25, andthe air bag body 1 is partly restricted in the height direction, and isslidable in the radial direction. After this state, when increasing theinternal pressure of the air bag body 1, the upper blades 26 whichcontact with the expanding air bag body 1 move upward so as to move theupper and lower panels 12 and 11 apart from each other. However, theupper plate blades 26 are kept at a height at which the upper panel 12of the air bag body 1 is not in contact therewith.

Next, as an accumulating step, each of the movable blocks 24 isinterlocked and is moved forward so as to be gathered toward the centerpoint 0 at the same time. Each of the blocks 24 moves to the forwardmovement limit shown in FIGS. 10 and 11 via an intermediate state shownin FIG. 9. In FIG. 9 schematically showing the air bag body 1 in themiddle step of the folding, the air bag body 1 is structured such thatthe upper and lower panels 12 and 11 are folded so as to form a waveshape without substantially engaging with each other, that is, in aso-called “estrangement” from each other in the portion pressed by themovable block 24, and an expanding portion 31 protruding so as to form adome shape is formed in the center. A plurality of wave-like recessportions 32 is formed in the periphery of the expanding portion 31. Aplurality of tab portions 33 is formed in a portion gripped between theupper and lower blades 26 and 25. Accordingly, a whole shape of the airbag body 1 is formed in a substantially asterisk shape. In this case, inaccordance with the forward movement of each of the movable blocks 24,each of the tab portions 33 slides toward the center portion through theportion between the blades 26 and 25 together with the wave-like recessportion 32 corresponding to the accumulated portion, so that theexpanding portion 31 tends to be further protruded.

Next, as shown in FIG. 13, as a restriction reducing step, the upperblades 26 are set at the current position, and the lower blades 25 areretracted slightly downward or wholly. Accordingly, it is possible toweaken or do away with the force gripping the linearly guided tabportion 33 of the upper and lower panels 12 and 11, and is possible tokeep the shape of the air bag body 1 by the center plate 27 and themovable blocks 24. In this case, in the restriction reducing step, itmay be adopted to move the upper blades 26 upward by a slight amount.

Next, as shown in FIG. 13, as a pressing step, the center block 23holding the center portion of the air bag body 1 is rotated in adirection shown by an arrow C at a predetermined angle, Together withthis rotation, the tab portions are taken into the pressing portion 24 aside of the movable blocks 24, and are arranged along the outerperiphery portions of the wave-like recess portions 32 so as to form aspiral shape. The tab portions 33 are arranged therealong without beingdeformed upward by the upper blades 26, and the shape of the folded airbag body 1 is arranged at a predetermined height.

As a displacing step after the pressing step, the center plate 27 isdescended. As shown in FIGS. 15 and 16, the expanding portion 31expanding above the air bag body 1 is pressed down and accumulated so asto form in a flat shape. A front surface deploying portion 35 notengaging with the other portions is formed by covering the expandingportion 31 formed in a flat shape over the folded portion of the air bagbody 1, and is restricted to a height corresponding to a predeterminedreceiving size. After this state, as shown in FIG. 1A, the air bag body1 is folded in a predetermined shape having a substantially petal shape,and the shape of the air bag body 1 is arranged in a column shape of asubstantially regular octagon in plan view having a predeterminedheight.

For example, as in a folding apparatus 21 shown in FIGS. 17 and 18, withrespect to each of the lower blades 25, there are provided a first guideportion 25 b in which an upper end edge portion thereof is parallel tothe table 22 front surface, and a second guide portion 25 c descendingfrom an inner peripheral side end portion of the first guide portion 25b toward an inner peripheral side so as to form an inclined surface.With respect to each of the upper blades 26 having a height whollylarger than that of the lower blades 25, there are formed a first guideportion 26 b opposed to the first guide portion 25 b of thecorresponding lower blade 25 and being parallel to the first guideportion 25 b, and a second guide portion 26 c opposed to the secondguide portion 25 c of the corresponding lower blade 25. Further, in thesecond guide portion 26 c, a surface parallel to the surface of thetable 22 is provided in continuous relations with the inclined surfaceinclined toward the upper side, and is arranged so as to protrude to aninner peripheral side along the lower blade 25. In this case, to thefirst guide portions 26 b and 25 b and the second guide portions 26 cand 25 c corresponding to end portions at which the upper and lowerblades 26 and 25 are linearly in contact with the air bag body 1, anemboss work is applied or an elastomer tape or the like is adhered,whereby it is set that they are slidably in contact with the air bagbody 1 with the proper sliding resistance.

When the air bag body 1 folded in the manner mentioned above isassembled in the air bag apparatus, the inflator is operated and the gasis supplied from the inlet port 15 of the air bag body 1, at first thefront surface deploying portion 35 positioned immediately above theinlet port 15 is rapidly deployed to the front surface side, and breaksthe cover 5 so as to form the protruding port.

Next, the upper and lower panels 12 and 11 are easily moved apart fromeach other, and the tab portions 33 arranged along the outer peripheryof the wave-like recess portions 32 in the folding final step arepressed to the outer peripheral side, whereby the air bag body 1 can berapidly deployed. In that event, the supplied gas is smoothly suppliedalong the portions restricted by the opposed upper and lower blades 26and 25 to the end portion of the tab portions 33, and the tab portions33 are deployed so as to be unwound, whereby it is possible to easilyimprove the deploying characteristic.

In the folding apparatus 21 in accordance with the present embodiment,the portion corresponding to the upper blade 26 in the upper panel 12 ofthe air bag body 1 is linearly guided by the upper blade 26 along atrack accumulated by the movable block 24. The structure is made suchthat the portion other than the portion corresponding to the upper blade26 in the upper panel 12 can freely protrude without being restricted inheight. Since the whole surface of the upper panel 12 is restricted inheight, the structure of the air bag body 1 can be made simple, and itis possible to sufficiently move the upper and lower panels 12 and 11apart from each other at a time of expansion. Further, in the state thatthe air bag body 1 is folded, it is possible to make the upper and lowerpanels 12 and 11 not be engaged substantially with each other from theinlet port 15 to the peripheral edge portion 14.

Since the upper and lower blades 26 and 25 are retracted and the centerblock 23 is rotated after the accumulating step of moving forward eachof the movable blocks 24, it is possible to reduce the force applied tothe upper and lower panels 12 and 11 and it is possible to smoothly foldthe air bag body 1.

Since the front surface deploying portion 35 provided in the centerfront surface of the air bag body 1 deploys at the beginning so as torapidly break the cover 5, it is possible to effectively utilize thepressure of the gas injected from the inflator so as to rapidly deploythe air bag body 1, and it is possible to make the air bag apparatuscompact. Since it is possible to reduce the primary peak pressure of theinjection gas, it is possible to increase the secondary peak pressure ofthe injection gas and it is possible to effectively utilize the gaspressure of the inflator. At a time of deploying the air bag body 1, theair bag body 1 is deployed so that the expanding portion 31 can bereformed due to the gas pressure from the front surface deployingportion 35, and the front surface deploying portion 35 can smoothlybreak the cover 5 formed by using a soft resin or the like. Further, itis possible to easily adjust the passenger restraining characteristic byreducing the internal pressure (the primary pressure), reducing theimpact and deploying in the peripheral direction, in accordance with thedeployment of the front surface deploying portion 35.

As mentioned above, in accordance with the air bag body 1 and the airbag apparatus using the air bag body 1 of the present embodiment, it ispossible to rapidly deploy and it is possible to easily improve thedeploying characteristic. Further, in accordance with the method offolding the air bag body 1 suitable for automation and the foldingapparatus 21 to which the method of folding the air bag body 1 isapplied of the present embodiment, it is possible to reduce theproduction cost of the air bag body having the improved deployingcharacteristic and it is possible to inexpensively provide the air bagbody.

In accordance with the embodiment mentioned above, with respect to eachof the lower blades 25 and each of the upper blades 26, the guideportions 25 a and 26 a parallel to each other are provided, however, itis possible to change the shape of the guide portions so as to intend tosmoothly guide the air bag body 1 in the folding step.

In each of the embodiments mentioned above, after the accumulating stepof forward moving each of the movable blocks 24 and the pressing step ofrotating the center block, the displacing step of descending the centerplate is executed. The structure can be made such that after theaccumulating step of forward moving each of the movable blocks 24, thedisplacing step of descending the center plate is executed so as to formone upper panel 12 in a substantially flat surface shape at the portionopposing to the inlet port 15 of the lower panel 11 and next, thepressing step of rotating the center block 23 is executed, therebyfolding the air bag body 1. In this structure, the upper panel 12 isarranged by one sheet in a substantially flat surface shape withoutbeing folded, at the portion opposing to the inlet port 15 of the lowerpanel 11. Accordingly, the gas introduced from the inlet port 15 issmoothly supplied to the outer peripheral side from the portion near theinlet port 15, and it is possible to smoothly deploy the foldedwave-like recess portions 32 and the tab portions 33 toward the outerperipheral side.

Further, in each of the embodiments mentioned above, in the restrictingand expanding step, the height of the air bag body 1 is restricted bythe upper and lower blades 26 and 25 after expanding the air bag body 1.In addition to the structure mentioned above, it is possible to employan operating step of expanding the air bag body 1 after restricting theheight of the air bag body 1 by the upper and lower blades 26 and 25,and an operating step of restricting the height of the air bag body 1 bythe upper and lower blades 26 and 25 while expanding the air bag body 1.

The present invention mentioned above can be applied to an air bagapparatus for a passenger in an assistant driver's seat provided in aninstrument panel, an air bag apparatus for a side protection provided ina side portion of a seat or a door and a pillar of a vehicle body, anair bag apparatus for a rear passenger provided in a rear portion of theseat, the other air bag apparatuses for protecting a subject to beprotected from an impact, and the like, in addition to the air bag bodyfor the air bag apparatus provided in the steering wheel of the motorvehicle.

What is claimed is:
 1. An air bag comprising: an inlet port throughwhich gas is introduced into said air bag; a plurality of wave-shaperecess portions, being accumulated and folded in a wave-shape patterntoward the inlet port; a plurality of tab portions formed between thewave-shape recess portions, being wound along the wave-shape recessportions; and a front surface deploying portion opposed to the inletport; wherein the air bag is made of a first surface portion and asecond surface portion each having a circular shape, being sewn at aperiphery thereof to form a bag shape, and the first surface portion isnot engaged with the second surface portion substantially in regions ofthe wave-shape recess portions.
 2. An air bag according to claim 1,wherein: the front surface deploying portion is accumulated so as to beformed in a flat shape without engaging with the wave-shape recessportions and the tab portions.
 3. An air bag apparatus comprising: anair bag and a cover, the air bag including; an inlet port through whichgas is introduced into said air bag, a plurality of wave-shape recessportions, being accumulated and folded in a wave-shape pattern towardthe inlet port; a plurality of tab portions formed between thewave-shape recess portions, being wound along the wave-shape recessportions; and a front surface deploying portion opposed to the inletport; wherein the cover covers the front surface deploying portion and aside surface of the air bag; the cover having a breakable surfaceopposed to the front surface deploying portion; the air bag is made of afirst surface portion and a second surface portion each having acircular shape, being sewn at a periphery thereof to form a bag shape;and the first surface portion is not engaged with the second surfaceportion substantially in regions of the wave-shape recess portions. 4.An air bag apparatus according to claim 3, wherein; the front surfacedeploying portion is accumulated so as to be formed in a flat shapewithout engaging with the wave-shape recess portions and the tabportions.